"Tevez is absolutely key to City's hopes, both in this match and for the rest of the season," Rosler, who scored twice against United in the Manchester derby during a four-year spell at the club from 1994-98, told BBC Sport.

"He'll be desperate to shine against his former club and knows this is a golden opportunity for City to step up their title bid. The statistics show he's probably their most important player and, while we don't know the full story behind his departure from Old Trafford, United may regret not keeping him.

"He is a striker who can dribble, turn a man, chase non-stop, press the opposition, make smart moves, hold the ball up and - crucially - score goals. He is always up for it, has bags of energy, wears his heart on his sleeve and gives the whole team a lift.

"For me, he is every manager's dream and the perfect player for English football."

Tevez is set to face his old side for the fourth time since swapping red for blue and the match provides him with another chance to show Sir Alex Ferguson exactly what he is missing out on.

Despite his success and popularity during a two-year spell at United, Ferguson was reportedly unwilling to spend £25.5m on a player who made 26 of his 97 appearances for the Old Trafford club as a substitute.

And for a manager who expects players to come off the bench and make an impact - Ole Gunnar Solskjaer immediately springs to mind - his decision was perhaps understandable.

Tevez plundered 30 goals in 71 starts for United (a goal every 2.3 games) but only four in 26 substitute appearances (a goal every 6.5 games).

Clearly unhappy with this bit-part role, he became the first high-profile player since Denis Law in 1973 to cross the divide, joining a club who were happy to meet the asking price and position him at the pinnacle of their Abu Dhabi-funded revolution.

Suffice to say, Tevez has not looked back.

Highlights - Man City 2-1 Man Utd

He scored nine goals in 18 games before
Mark Hughes was sacked
in December 2009 and, despite voicing his displeasure at the Welshman's dismissal, made a superb start to life under new boss Roberto Mancini.

A return of nine strikes in his next six starts and a further 11 before the end of the campaign saw Tevez finish with 29 goals as he led City to within three points of a top-four finish.

End-of-season calculations showed City were almost twice as likely to emerge triumphant with Tevez in the team (they won 55% of their matches when he played and just 33% in his absence).

The 26-year-old's importance was illustrated in February when Mancini's men drew three and lost one of their four matches
while he was in Argentina
caring for his baby daughter, who was born prematurely.

"City often appear to lack enthusiasm when Tevez isn't in the side," observed Rosler, who scored 50 goals in 153 games for City and since retiring as a player has manager Norwegian sides Lillestrom, Viking and Molde.

"He lifts his team-mates and also the crowd through his style of play. In my time at City, Paul Walsh was similar: very busy, never giving up, chasing everything and always looking to create chances.

"In the game at Wolves in October [when Tevez was injured], City got an early goal and then played as if they thought the job was done. They invited Wolves back into the game and ended up losing.

"With Tevez in the team you have a guy who is up for it all the time and he carries the rest of the players with him."

The burden on Tevez has not been helped by the departure of Craig Bellamy, Emmanuel Adebayor's struggle for form, Mancini's reluctance to pick Roque Santa Cruz or a knee injury to new signing Mario Balotelli.

TEVEZ IN STATS

100%: City have won all five of the games in which Tevez has scored this season

91.6%: City have won 22 of the 24 games in which Tevez has scored since joining

56%: City have won 31 of the 55 games Tevez has played

37.5%: When Tevez has started, 36 of City's 96 goals have come from the Argentine

26.6%: City have won just eight of the 30 matches in which Tevez has not scored

1.4: Tevez has scored 36 goals in 51 starts for City, averaging a goal every 1.4 games

6.5: Tevez scored four goals in 26 substitute appearances at Old Trafford, a goal every 6.5 games

Statistics correct as of 09/11/10

But Tevez has responded again this season, the man from Buenos Aires scoring five goals in 13 games, providing three assists and taking far more shots than any of his team-mates.

City have won all five of the matches in which he has scored, whereas in the eight matches he has not, City have won three, drawn three and lost two. In fact, City are yet to lose a league game in which Tevez has scored.

"There is a big difference between City with Tevez and without him," said Rosler. "When he was injured recently, Adebayor came in and scored goals but City were poor.

"They are hugely different players. Tevez is always on the move and and available, constantly giving the opposition a headache.

"To me, Adebayor sometimes looks very lethargic and static."

Mancini's decision to
hand Tevez the captain's armband
this season suggested he views the former Boca Juniors, Corinthians and West Ham star as his natural leader on the pitch.

The argument was thought to have revolved around City's tactical formation, with Tevez frustrated at Mancini's decision to play him as a lone striker throughout the early part of this season.

He also irked his manager by claiming the prospect of
early retirement had crossed his mind,
by making fairly regular trips back to Argentina and by speaking of a longing to be with his family in his homeland.

"The only thing that worries me is that he has come out in public a few times to say he misses Argentina, he misses his family, he thinks about retiring," said Rosler, who plans to move his family back to Manchester having completed a successful two-month stint at Molde.

"Whether or not he gets on with Mancini is irrelevant because that is not affecting his performances; in fact, Mancini seems to be getting the best out of him. What City don't want is to hear more talk of homesickness.

"They have invested a lot of money in Tevez, he is playing very well, the players look up to him and the fans adore him. If he was to leave it could have a disastrous affect on City's entire project."

City will be hoping on Wednesday night it is United's Premier League project on which Tevez can have a disastrous effect.

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